This invention relates to a rotary drive apparatus for a rotary downhole pump and particularly to an improvement in the connection between the rotary drive apparatus and a rotary drive string extending downwardly in a well to the pump.
Rotary pumps as distinguished from the reciprocating plunger type have been used in water wells for many years and more recently have proven beneficial for pumping wells bearing crude oil laden with sand. In relatively shallow water wells only limited axial adjustment of the rotary drive string is required with respect to the rotary drive apparatus. Therefore, a threaded rod and nut connection between the rotary drive apparatus and rotary drive string is suitable. Examples of this type of connection are shown in various catalogs of the Peerless Pump Division of the FMC Corporation. Also, conventional rotary couplings such as shown in U.S. Pat. No. 4,087,211, Pochyly, may be used, but have the same drawback with respect to axial adjustment as the threaded connection just mentioned. Significantly, greater axial adjustment as required for connection to deep oil well production strings is provided by the use of a slidable polish rod clamp as shown in U.S. Pat. No. 4,372,379, Kulhanek et al. However, accidential release or slippage of such a clamp type connection may result in loss of the rotary drive string down the well which can cause damage to the well and the down hole equipment located therein. Also, repair or adjustment of the rotary drive assembly or motor cannot be made without removal of the string or holding it in place with auxiliary equipment.
Therefore, it is a primary object of this invention to provide an improved rotary drive apparatus for rotary downhole pumps which permits significant axial adjustment of the rotary drive string and prevents accidental loss or slippage of the string in the well.